The China Internet Illegal Information Reporting Center had told Google to “make immediate changes" and clean up the content available through its search engine (www.google.cn), the official Xinhua news agency reported.

The targeting of Google illustrates the difficulties faced by foreign Internet firms doing business in the world's largest online market while avoiding charges of censorship.

In an emailed statement, Google said it met with government officials to discuss the problem of “pornographic content and material that is harmful to children on the web in China."

“We are undertaking a thorough review of our service and taking all necessary steps to fix any problems with our results. We believe we have addressed a large majority of the problem results," the statement said.

The order came a day after Chinese state television blasted Google and the center denounced it for allowing “foreign Internet pornographic information."

The Chinese government recently ordered all new personal computers to carry Green Dam filtering software designed to block pornographic Internet content from July 1, leading to fears China was using its campaign to protect children from “unhealthy" content as a way of tightening censorship.

Google has been “ordered to comply with China's laws and regulations and completely filter pornographic content to prevent pornographic material from entering from overseas," Xinhua said.

The order coincides with plans by the city of Beijing to recruit tens of thousands of volunteers to monitor the Internet.